> For the complete documentation index, see [llms.txt](https://dexiejs.typogram.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dexiejs.typogram.co/promise/promise.onuncatched.md).

# Promise.onuncatched

Called if the promise wasn't caught.

***Deprecated. This event is deprecated and obsolete since 4.x***

**Sample**

```javascript
var p = new Promise(function (resolve, reject) {
    reject("Failed!");
});
p.onuncatched = function (e) {
    alert ("No-one caught this error: " + e);
}
```

Result:

Since neither `then(x, f)`, `catch(f)` or `finally(f)` was called with a valid function f, the alert would be fired.

**How this is used in Dexie**

Dexie uses this event on all returned promises from any DB operation on a Transaction in order to make sure error is propagated to the transaction and that transaction is aborted.